Shimano 1:1 ratio rear deraileur conversion.

I've been running XT/XTR for the past three and a half years it has always performed flawlessly (well the LX didn't but that was gooped up cables that I never changed, cleaned, or lubed)..... until recently.

I did crash and bend the derailer hanger and/or the deraileur cage a month or so back and finally got things mostly straightened out and readjusted so it was shifting pretty well again, but then I broke a cable and since I've put the new one on following Sheldon Brown's setup instructions and a week or so of perfect shifting, it's now doing a couple of funny things. Not sure where to go with the adjustment. A little help from the gurus would be appreciated.

Disclaimer: I'm no bike mechanic... but there is no bike mechanic within 200 miles of my house so I'm all I've got..... well, me and you.

Here's the problem:

It seems to be indexing fine as far as no grinding noise while it's in any of the cogs, but it sometimes requires two clicks before it will shift down onto a smaller cog (usually between the third and fourth or fourth and fifth cog). It also seems sluggish shifting up onto the next bigger cog... pushing on the thumb trigger... nothing happening... push a little further then it goes or maybe it jumps up two. But like I said once it's on the cog there's no sound of maladjustment.

This post makes no sense. Shimano derailers are 2:1 actuation ratios. What are you talking about as far as the 1:1?? What "conversion" are you talking about?

Your problem sounds like it would be most likely attributed to a poor installation of new cable/housing. If somewhere a small strand of cable is broken and dragging in the housing, it would cause the problems you are talking about. Also kinks in the cable or in a crimped ferrule would be sources of friction that could be causing the problem.

Bent derailers can also do what you are talking about. Even though the bend may not be visable, bent derailers can sometimes be adjusted to work ok for a few hours, and then they go pretty "wild". I ran into this problem as a shop mech, and we were at wits end trying to figure out what was wrong with a customer's bike. The customer had a shop in Phoenix work on it, and when he got it back, it would never stay in adjustment more than a few hours, and it would just go crazy. I narrowed the problem to the derailer, and changed the derailer..no more problem. Bending back derailers or derailer hangers can work in a pinch for the rest of a ride, but in the long term the hanger or derailer is probably toast and needs to be replaced, even if it "looks" good with the naked eye.

"It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

It seems to be indexing fine as far as no grinding noise while it's in any of the cogs, but it sometimes requires two clicks before it will shift down onto a smaller cog (usually between the third and fourth or fourth and fifth cog). It also seems sluggish shifting up onto the next bigger cog... pushing on the thumb trigger... nothing happening... push a little further then it goes or maybe it jumps up two. But like I said once it's on the cog there's no sound of maladjustment.

Where should I start?[/QUOTE]

Sound like your new cable is to blame. Was it a quality cable ? Cut correctly ?

It seems to be indexing fine as far as no grinding noise while it's in any of the cogs, but it sometimes requires two clicks before it will shift down onto a smaller cog (usually between the third and fourth or fourth and fifth cog). It also seems sluggish shifting up onto the next bigger cog... pushing on the thumb trigger... nothing happening... push a little further then it goes or maybe it jumps up two. But like I said once it's on the cog there's no sound of maladjustment.

Have you replaced the cable housing? Gummed up housing can lead to the behavior you describe.

One thing to check...

Make sure the cable is clamped on the correct side of the pinch bolt on the derailleur. Sounds trivial, but it's not. The distance the derailleur moves with each click is very different if the cable is clamped wrong there. You can actually mate Campy with Shimano by intentionally clamping the cable incorrectly.

Have you replaced the cable housing? Gummed up housing can lead to the behavior you describe.

The housing is Avid Flak Jacket that I put on a little over a year ago. I just replaced the cable. The idea of cable stretch crossed my mind, but now that you mention it, it does seem like more effort is required at the shifter.

Is all deraileur cable the same diameter? Or could the cable be unraveling inside the housing?I guess the housing could be getting mucked up. What's the best way to clean it if taking up extra cable slack doesn't solve the probelm? Or should I just replace it?

Hmmm... I think this all screams of bent hanger and bad housing. You don't "mostly" straighten out a derailleur hanger. It has to be perfectly straight to give acceptable performance. Also note that once hangers get bent and restraightened the weaken alot and can bend back out of shape by the simple derrailleur tension and bouncing.
Finally I think the housing has a lot to do with it. I've used flack jackets in the past and its the single kind of cable I would NOT recommend. I don't know why but in the year I used it I got some really bizzare behavior with that kind of housing. It worked beautifully for about 2 weeks and then started going downhill from there on. Its so stiff it just doesn't seem to conform too well when parts like the bars and derailleur move. It pinches the cable. Its so stiff the cable also seems to grind away at the inner lining very easily gumming everything up. Overrated cable IMO.

I recommend you do a full cable and housing change. You mentioned its over a year old so its overdue for it anyway. Try to buy a new derailleur hanger as well. Straightening a hanger should normally be a temporary fix to keep you going until you can replace it.

I had a chance to do a bit of work on my rear derailleur and cable this weekend and it definitely was a combination of sticky cable/housing and a slightly bent hanger. I pulled the cable and wiped it down with a rag and silicone spray. I then forced WD40 down through the housing and reassembled. It still wasn't shifting exactly right, but at least it wasn't hanging.

I then took a good look at the hanger and decided it was bent inward slighty so took the derailleur off and straightend it. Reassembled, adjusted cable tension and voila'.....my crisp, accurate, XTR shifting was back (oh, and the trigger effort was much improved).

I suspect this fix is only temporary, but at least I'm back and running for now.

I then took a good look at the hanger and decided it was bent inward slighty so took the derailleur off and straightend it. Reassembled, adjusted cable tension and voila'.....my crisp, accurate, XTR shifting was back (oh, and the trigger effort was much improved).

I suspect this fix is only temporary, but at least I'm back and running for now.

You should be in the process of ordering a new derailer hanger, that's what you need to do to fix this problem. Bend derailer hangers that were bent back will now be too soft and will get easily bent in the future, so a new hanger is needed.

"It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth